Finned tube



Aug. 15, 1944. J. w. BROWN, JR

FINNED TUBE Filed April 2, 1941 2 Sheets-Sheet l "Ill INVENTOR.

Aug. 15, 1944. J. w. BROWN, JR

FINNED TUBE Filed April 2, 1941 2 Sheets-Sheet 2 INVENT OR.

A 7'7'OP/VEY5 m W a w N E H "WWW Patented Aug. 15, 1944 FINNED TUBE John W. Brown, Jr., Lakewood, Ohio, assignor to Brown Fintube 00., Elyria, Ohio, a corporation of Ohio Application April 2, 1941, Serial No. 386,503

10 Claims.

This invention relates to heat exchanger tubes and method of making same and more particularly to tubes provided with exterior flns for increasing the external surface area thereof.

In my prior applications Serial No. 323,593, filed March 12, 1940, and Serial No. 380,690, filed February 26, 1941, now respectively Patent No. 2,298,249, issued October 6, 1942, and Patent No. 2,261,137, issued November 4, 1941, I have disclosed heat exchanger tubes having fins secured to the exterior thereof and methods and apparatus for making such tubes. The tubes specifically disclosed in said applications were particularly adapted to installations wherein the flow of fluid on the exterior of the tube was longitudinal. The present application relates more specifically to heat exchanger tubes adapted for transverse flow of fluids on the exterior thereof, or to form wall structures, partitions, and the like.

It is among the objects of the present invention to provide such a tube which will be eifioient in its heat exchange characteristics and.

which will have the ability to withstand severe operating conditions for long periods of time. Another object is to provide a tube which may be made more or less streamlined for transverse flow. Another object is to provide a tube of this character which can be manufactured rapidly and economically. A further object is to provide an efficient and economical method of and apparatus for making such tubes. Further and more specific objects of the invention will become apparent from the following description of various forms thereof being made to the accompanying drawings. The essential characteristics are summarized in the claims.

In my prior applications aforesaid, I disclosed tubes wherein channel members were secured to the exterior of the tube. In the preferred embodiment shown in said applications each channel member formed two generally radially extending fins. tion, one or more channel members may be secured to the exterior of the tube as by resistance welding, or otherwise autogenously welding the base portions thereof to the tube, and thereafter the channel membersare deformed so that each- According to the present inven-.

the of a preferred form of finned tube made according to my invention and embodying longitudinally extending fins on diametrically opposite surfaces of the tube; Fig.2 is a transverse section through the finned tube of Fig. 1 showing the tube as it appears at. an early stage in the manufacturing process; Fig. 3 is a similar section illustrating the tube as it appears after a sub-.

sequent step has been carried out; Fig. 4 is a transverse section through a modified form of I ;spectively, of an apparatus adapted to carry out my method and manufacture the tubes illustrated in Figs. 1 to 7, the apparatus shown being specifically adapted to the production of the tube shown in Figs. 1 to 3.

A preferred form of my invention as illustrated in Fig. 1 of the drawings may comprise a tube Ill having fln members indicated generally at H secured to the exterior thereof at diametrically opposite points. Each fin member preferably comprises a base portion [2 welded as indicated at [3 or otherwise suitably secured to the exterior of the tube and two flange portions I4 extending from and formed integrally with the base por tions, the flange portionsbeing bent toward each other and preferably welded together adjacent their outer edges as indicated diagrammatically at I5 so that the flanges arejoined together to form a single fin having an open space I6 therein. Those skilled in the art will appreciate that for some purposes it will be preferable to secure only a single member II to the tube and that for other purposes it may be desirable to secure more than two such members to the exterior of the tube. However, with two.oppositely disposed fin members as illustrated in the drawings, the tube lends itself particularly touse in posed to the gases or fluids on the exterior of the tube insures that heat will be conducted from the flanges to the tube at a high rate with respect to the rate of absorption of heat by the flanges. Thus, the durability and resistance to corrosion of the flanges is excellent, even though single heavy gauge flanges were employed, difliculties have been encountered because of the fact that heat shocks have resulted inthe imposition of excessive strains on the tube and ultimately in failure of the tubes.

In Figs. 2 and 3 I have illustrated steps in a preferred method of manufacturing the tubing shown in Fig. 1. As shown in Fig. 2, the members I l are preferably initially in the form of open channels.' These are positioned on the tube as shown and are preferably welded thereto in the manner described in my prior applications aforesaid by electrode rolls en agi g the bases 12 of the channels and arranged to produce autogenously welded areas IS with their centers substantially evenly spaced along the bases l2 and arranged to insure adequate paths for the transfer of heat between the tube, the base portions l2 and the flanges 14. After the welding operation has been completed, the flanges H are bent toward each other to produce the structure illustrated in Fig. 3, thereafter the flanges are welded as at, I! adjacent their outer edges, these welds being either continuous or spaced any convenient distances apart, say about /2 inch in a tube of the general size shown in the drawings. For most purposes it is not necessary to provide a continuous weld between the flanges, although for some services such a weld may be required or preferred.

P; eferably the operations of welding the chanml: to the tube, deforming the channels and welding the flanges of the channels together are carried out continuously in an apparatus such as that diagrammatically illustrated in Figs. 9 and 10. Such an apparatus may comprise a suitable base or fram (not shown) supporting a series of rolls for carrying out the various operations and for guiding the tube and channels through.

the apparatus. The tube and the channels I l are progressed. through the apparatus in the direction of the arrow and the tube and channels are first entered between the guid rolls 2|, which engage the external surfaces of the tube, and the guide rolls 2|, which enter the channels to guide and align the channel members with respect to the tube before they are welded thereto. Next, the tube is engaged by a second series of guide rolls 22, while disposed adjacent to these rolls there are electrode rolls 23 suitably" connected to a source of current which is controlled preferably in the v manner described in my aforesaid applications to produce rows of intermittent welds between the bases l2 of both member H and the tube. The electrode rolls preferably .engage the-bases l2 of the channels and the arrangement is such that the current flows from one electrode roll 23 through the channel bases and tube to the other roll 23, effecting simultaneous welding of oppothe channel guide rolls 2!. The tube sitely disposed areas between the tube and the bases of the respective channels.

The tube with the channels secured thereto then passes between the tube guide ro'ls 24 and at this point has the cross-sectional appearance illustrated in Fig. 2 and is preferably substantially identical with the tube described and claimed in my aforesaid application Serial No. 380,690; 1. e., the welded areas l3 are so shaped and proportioned that the path for the flow of heat from the tube through the welded areas and into the base of the channel i at least substantially as great as the path for the transfer of heat from the base of the channel to the flanges. This is preferably accomplished by making the total welded area at least substantially equal to the combined longitudinal cross-sectional area of the flanges adjacent the base, and the total perimetric length of the welded area at least substantially al to, and preferably greater than, twice the length of the channel, as described in detail in my application Serial No. 389,690 aforesaid. The tube, with the channel members secured thereto, is then passed-between a pair of forming rolls 26 which, as illustrated in the drawings, are provided with central reduced portions 21 to receive the tube and tapered portions 2! and cylindrical portions 29 to engage the flanges I4 and force them together into the form shown in Fig. 3.

The tube is completed by being passed between pairs of flange welding rolls in which engage the flanges liand H of members II and which are connected with suitable sources of electricity (not shown)v to produce the welds II shown in Fig, 1. In each of the welding operations the pressure of the electrode rolls and the flow of current and the timing are properly correlated to produce the desired character of weld. The timing of the flow of current is preferably controlled by thyratron controls which accurately time the current to produce welds of the desired duration. Thetube may be progressed through the machine by driving the electrode rolls 23, the forming rolls 28 and the electrode rolls ll at substantially the same peripheral speeds by any convenient mechanism. The tube then passes through the final guide rolls ii and is discharged from the machine.

- From the foregoing, it will be evident that tubing according to my invention can be produced rapidly and economically by a single, apparatus which carries out my method continuously. In practice, the operation can be carried out at speeds 0120 to 25 feet per minute without dlfllculty and by reason of the fact that in the preferred form identical welding operations are performed on opposite sides of the tube, the completed tube is straight and free from destructive strains.

In Fig.4 of the drawings I have illustrated a tube which is particularly adapted for boiler wall structures, this tube comprisin the central tubular member 22 with fln members 33 secured to diametrically opposite surfaces thereof. The fln members 32 are generally similar to the members ll heretofore described in that they comprise base portions ll welded to th exterior of the tube II and flanges ll extending therefrom and welded together near their outer edges, as indicated at 26. The fin members differ from those previously described in that the flanges 35 are bent so that'nearly all of their inner surfaces are in engagement with each other, there being only a very small space 31 between the flanges immediately adiacent the base portions 3. This type .of structure is particularly adapted for boiler walls, it being possible to weld a series of flanges of this type together to form a continuous wall structure. Because of their strength and rigidity, these tubes, as well as' the other forms shown herein, may be used with advantage as structural members in environments where their heat exchange ability is not important. Such tubes are also adapted for some services where there is a longitudinal flow of fluid along the exterior of the tubes and very severe operating conditions. Tubes of this type may be manufactured as described heretofore with the abafter the channel has been welded to the tube and formed into the shape shown. The slots may be punched in the fins or sawed or formed in other ways well understood by those skilled in the art. They may be extended to varying may be varied depending upon the service for paratus shown in Figs. 9 and 10, it only being necessary to change the shape of the forming rolls to conform to the desired shape of the fin members.

In Figs. 5, 6 and 7 I have illustrated a further modification of my invention wherein the tube 40 is provided with fin members 4|, the bases "of these fln members being much wider than the bases shown in Fig. 1 in proportion to the circumference of the tube so that the fin members extend around a considerable proportion of the tube and provide a greater streamlined effect than the constructions illustrated in Figs. 1 and 4.

'In manufacturing tubes of this sort, the base portions 42 are preferably curved to conform to the tube and may be welded to the tube by a series of centrally disposed welded areas indicated diagrammatically at 43 and preferably produced as described in my aforesaid applications. If the operating conditions are severe and the heat load is great, additionalrows of welds as indicated at 44 and 45 may be provided. In case such additional welds are deemed necessary, additional welding rolls will be required in the apparatus or it may be necessary to pass .the tube through the fin welding apparatus more than once. However, the general principles of the welding apparatus and the method employed in manufacturing such tubes are identical with those heretofore described, the channel members first being welded to the tube, then formed into the shape shown and finally the flanges 46 are welded together adjacent the outer edges thereof as indicated particularly at 48. Obviously, the shape and proportions of the flns may be varied from the forms shown-herein, depending on the requirements of the service for which the tube is intended.

In Fig. 8 of the drawings I have illustrated a further modification of my invention as applied to a finned tube 31a of the type illustrated in Fig. 4. According to this modification of my invention, the flanges 35a and the fins 33a, which are otherwise similar to the fins 33 shown in Fig. 4, are slotted as indicated at 49, from their outer edges inwardly toward the base portions 34a. The reason for this is that under some sever operating conditions there may be a large temperature difference between the tips or outer edges of the fins and the bases thereof. Because the tips of the fins under such conditions will be at a considerably higher temperature 'than the base portions of the fins, the outer which the tube is intended, close spacings being employed for the more severe services. *In general, however, slots spaced and proportioned as shown with respect to the size of the fins will be satisfactory for manysinstallations.

While I have illustrated this feature of my invention only in conjunction with a finned tube of the type shown in Fig. 4, those skilled in the art will appreciate that it may be applied to finned tubes of various other types such as tubes of the type illustrated in Fig. l or tubes embodying channel section fins such as shown in my prior applications aforesaid.

From the foregoing descriptionjof preferred forms of my invention it will be evident that I have provided finned tubing adapted for use in heat exchangers where there is a transverse flow of fluid externally of the tubes, and also adapted for a wide variety of other usessuch as wall structure, partitions and'the like and as struc- I tural members where strength and rigidity. are required. Tubes made according to preferred forms of my invention have excellent heat .exchange characteristics and are-durable under severe operating conditions. The tubes can be produced rapidly and economically particularly by the preferred method and apparatus disclosed herein. I

Reference is hereby made to my divisional ap plication for Apparatus for manufacturing finned tubes, Serial'No. 544,713, filed July 13, 1944, which contains claims directed to the apparatus disclosed herein.

Various changes and modifications in my invention will become apparent to those skilled in the art. It is, therefore, to be understood that my patent is not limited to the preferred forms described herein, or in any manner other than by the appended claims when given the rang of equivalents to which my patent may be entitled.

I claim:

1. The method of making finned tubes which includes the steps of resistance welding the base of a channel section member having a base and two flanges extending therefrom to the exterior of a tube, thereafter bending said flanges toward each other to bring at least the outer edges thereof into contact with each other, and welding said edges together.

2. The method of making finned tubeswhich includes the steps of resistance welding the base of a channel section member having a base and two flanges extending therefrom to the exterior of a tube, thereafter bending said flanges into contact with each other, and permanently securing said flanges together. I

3. The method of making finned tubes which includes the steps of resistance welding the base of a channel section member having a base and two flanges to the exterior surface of a tube, controlling the welding current to produce a series of welded areas disposed between said flanges and of a combined area at least substantially equal to the combined longitudinal cross-sectional area of the two flanges, the total perimetric length of said welds being at least substantially equal to twice the length of the channel member, thereafter bending said flanges toward each other to bringat least the outer edges thereof into contact with each other, and welding said flanges together.

4. The method of making finned tubes which includes the steps of simultaneously resistance welding the bases of separately formed channel section members each having a base and two flanges extending therefrom to oppositely disposed portions of the exterior of a tube, then simultaneously bending the flanges of each channel inwardly toward each other to bring at least the outer edges thereof into contact with each other, and thereafter simultaneously welding the contacting edges of both channel members together.

5. In combination, a tube of substantially uniform wall thickness and a closed hollow fin secured thereto, said fin comprising a channel section member having a base portion and two flanges, the base portion substantially conforming to the outer surface of the tube and being joined thereto by autogenously welded areas, the flanges being bent into contact with each other and joined together.

6. In combination, a tube of substantially uniform wall thickness and a fin secured thereto, said fln comprising a member having a base portion and two oppositely disposed flanges extending therefrom, the base portion substantially conforming to the outer surface of the tube and being joined thereto byautogenously welded areas, the flanges being bent into contact with each other and welded together adjacent their outer edges.

'7. In combination, a tube of substantially uniform wall thickness and a closed hollow fin extending generally longitudinally thereof and secured thereto, said fin comprising a member having a base portion and two flanges, the base portion substantially conforming to the outer surface of the tube and being joined thereto by autogenously welded areas, the flanges being welded together adjacent their outer edges and spaced apart from a zone adjacent the welded portion to the base to provide a hollow fin having a generally triangular cross-section.

8. In combination, a tube of substantially uniform wall thickness and a pair of oppositely disposed closed hollow flns extending generally longitudinally thereof and secured thereto, each fin comprising a member having a base portion and two flanges, the base portion substantially conforming to the outer surface of the tube and being joined thereto by autogenously welded areas, the flanges being welded together adjacent their outer edges and spaced apart from a zone adjacent the welded portion to the base to provide a hollow fln having a generally triangular crossa section.

9. In combination, a tube of substantially uniform wall thickness and a longitudinally extending closed hollow fin secured thereto, said fln comprising a member having a base portion and two flanges, the base portion being curved to conform to the outer surface of the tube and covering at least about ninety degrees of the circumference of the exterior of the tube and being joined thereto by autogenously welded areas, the flanges being joined together adjacent their outer edges and spaced apart from a line adjacent the joined portions to their juncture with the base.

10. In combination, a tube of substantially uniform wall thickness and a longitudinally extending fin secured thereto, said fin comprising a member having a base portion and two oppositely disposed flanges extending therefrom, the base portion substantially conforming to the outer surface of the tube and being joinedthereto by autogenously welded areas, the flanges being bent into contact with each other and being welded together adjacent their outer edges, the inner surfaces of the flanges being substantially in contact from their outer edges to a zone closely adjacent the base whereby the fln has a generally T-shaped cross-section.

JOHN W. BROWN, JR. 

